In gas turbines, a hot gas flow is passed between two stator vane rings within a shroud ring. The shroud ring includes an outer shell and an inner shell, each of which are segmented. The number of outer segments is usually greater than the number of inner segments. Generally, gaps between the outer segments are located opposite central regions of inner segments. The gaps allow for thermal expansion of the outer segment and the inner segments. During operation, a portion of the hot gas flows into the gaps between the inner segments and heats up the end portions of the inner segments. The central regions are slightly cooler. Furthermore, cooling air flows through the gaps of the outer segments and impinges on the central regions of the already cooler inner segments. This results in high temperature gradients within the inner segments, causing cracks.
In order to overcome this problem, cover elements are placed over the gaps between the inner segments, the cover elements each being attached to an inner segment and extending over an adjacent inner segment. However, there is still leakage of hot gas, whereby the circumferential end portions of the inner segments are heated to a greater degree than the central regions. Alternatively, the inner segments are reinforced, which, however, increases the weight of the inner segments.
German publication DE 602 13 538 T2 describes a gas turbine having inner shroud segments and outer shroud segments. Cooling air flows through gaps between the inner shroud segments from the outside to the inside in the radial direction of the gas turbine to prevent hot gas from entering the gaps and heating the circumferential end portions of the inner shroud segments. The disadvantage here is the complex geometry of the end portions of the inner shroud segments, which requires increased manufacturing effort.
U.S. Pat. No. 7,604,453 B2 discloses a gas turbine having outer and inner cover segments forming a shroud assembly between a first row of stator vanes and a high pressure turbine section. Cooling air flows from the outside to the inside in the radial direction of the gas turbine through a gap located between the outer platforms of the row of stator vanes and the inner ring. Moreover, the inner cover segments are cooled by impingement cooling, convection cooling and film cooling. It is a disadvantage here that the inner and outer cover segments have a very high degree of structural complexity, which requires increased manufacturing effort.
European publication EP 0 959 230 B1 describes a gas turbine where inner ring segments downstream of a ring of high pressure guide vanes are cooled by impingement cooling, convection cooling and film cooling. Here too, the structural geometry is complex and requires considerable assembly effort.
U.S. Pat. No. 5,470,198 relates to a gas turbine which has a seal assembly located between combustion chamber discharge nozzles and an first ring of guide vanes and which uses cooling air flows. The seal assembly is specifically designed for this application.